With respect to super-hard materials such as diamond, sapphire (aluminum oxide), silicon carbide, boron carbide, tungsten carbide, silicon nitride and titanium nitride, smooth surfaces are typically obtained by polishing (lapping) processes in which diamond abrasives are supplied to platens for polishing. However, in a lapping process using a diamond abrasive, the formation of scratches and leftover scratches are limiting factors in increasing the surface smoothness. Thus, studies are underway for a polishing process that is carried out after or instead of diamond lapping, using a polishing pad and polishing slurry supplied to the interface between the polishing pad and an object to be polished. Publications disclosing this type of conventional art include Patent Documents 1 to 5.